The flurry of signings was announced by the Blazers on Friday while speculation continued to swirl about restricted free agent Nicolas Batum.
Hickson was claimed by the Blazers off waivers from Sacramento last March and played in 19 games for Portland, averaging 15.1 points and 8.3 rebounds. He was signed to a one-year deal.
Freeland, a 2006 draft pick by the Blazers, averaged 12.9 points and 7.5 rebounds last season with Unicaja Malaga of the Spanish ACB League. The 25-year-old center-forward is a starter for Great Britain's national team, which is competing in the London Games as the host nation.
The Blazers took Lillard out of Weber State with the sixth pick before selecting the 7-foot-1 Leonard out of Illinois with the 11th pick in the June draft.
Lillard, a two-time Big Sky Conference player of the year, averaged 24.5 points, 5.0 rebounds and 4.0 assists as a junior with the Wildcats. New Blazers general manager Neil Olshey called him the team's "franchise point guard" on draft night.
Leonard averaged 13.6 points and 8.2 rebounds as a sophomore last season. He led the Big Ten with an average of 1.9 blocks per game.
The Blazers have said they will match any offer for Batum, who was being courted by the Minnesota Timberwolves. The French swingman has averaged 10.2 points and 3.9 rebounds over four seasons with Portland.